Replace ZstdInterceptor with CompressionInterceptor (#9336)

* Replace ZstdInterceptor with CompressionInterceptor

* Gzip as fallback

---------

Co-authored-by: Jesse Wilson <jesse@swank.ca>

Author: HeroOussama

okhttp-zstd/README.md

@@ -9,7 +9,7 @@ Note that zstd is not used for sending requests.
 
 ```java
 OkHttpClient client = new OkHttpClient.Builder()
-  .addInterceptor(ZstdInterceptor.INSTANCE)
+  .addInterceptor(CompressionInterceptor(Zstd, Gzip))
   .build();
 ```